17-4 elongation, what do I need for 45000 rpm?

[007hammer]

elongation should have been 12% came out 10%

 

[NickE]

HUH?

You really are going to have to give us more information. To convert that rotational velocity to a load requires mass. (and probably some other things, mechanics is not my strong suit) To figure out if the extra 2% elongation before break is detrimental to your application is much more complex. What were the yeild and tensile strengths? Those are much more important under normal conditions than elong. @ Break. What condition is the material in? What is the specification for the material and condition?

There are many other hunchbacks (?) I could give you, It just depends on which soldiers (!) you're looking for.


Nick
I love materials science!

 

[israelkk]

What was the heat treatment? According to MIL-HDBK-5J for bars it is 12% for H1025 but 10% for H925 and H900. I do not think the elongation has to do with 45000RPM but if the elongation does not compatible with the material specification than it should not be used for aerospace use and should be returned to the manufacturer.

 

[007hammer]

Can't give much more info, matl ~3"od,1 3/4"L ultimate should be 150ksi, is 186; yield should be 135ksi, is 181; ra should be 45%, is 59; elongation should be 12% is 10.
Operational life ~~45min.
Can not redo to correct properties, use or loose it.

 

[Carburize]

Elongation is often used as a crude measure of toughness - i.e. the ability of the material to resist the presence of a flaw without failure - In the "old days" the concept was that "if I overload the part will it stretch far enough before it fails to warn me and give me time to get away!" A number of current standards use 10% as a minimum elongation value below which some evaluation of the toughness of the material may be necessary depending on the application.

In your case, it looks like the yield strength is way above the minimum specified and assuming that the operating stress is based on the yield stress and that you carefully inspect the part prior to use for any flaws I believe it will be OK.

 

[EdStainless]

I presume that you have retested?
Use full sized bars?
From center, mid-radius, or near edge?
Tried testing at various strain rates?

Why can't you re-do? It looks like this might benifit from a little overaging. A bit of time at a higher temp may help.

I don't like the very close UTS/yield. This is not good for fatigue and cracking.
Is there any historical data on impact or DCB crack testing?

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[Carburize]

Ed - in the post of Feb 22 it staes that the life requirement is 45 minutes which would be around 2 million cycles.It sounds like part of some kind of test equipment?